Vapor-deposited foamed body

ABSTRACT

A vapor-deposited foamed body having a film  15  vapor-deposited on the surface of a foamed plastic formed body  10  containing foamed cells  1  therein, wherein in the surface X of the foamed plastic formed body  10  serving as the under-layer on where the film  15  is to be vapor-deposited, the porosity of the foamed cells  1  is suppressed to be not more than 30% in the surface layer portion  10   a  to a depth of  50  μm from said surface. The vapor-deposited foamed body is obtained by vapor-depositing the film on the surface of the foamed plastic formed body such as a foamed container, the vapor-deposited film being uniformly formed and being effectively prevented from peeling off.

TECHNICAL FIELD

This invention relates to a vapor-deposited foamed body obtained byvapor-depositing a film on the surface of a foamed plastic formed bodysuch as a foamed bottle.

BACKGROUND ART

Containers made from a polyester as represented by polyethyleneterephthalate (PET) excel in such properties as transparency, heatresistance and gas-barrier property, and have been widely used for avariety of applications.

Some contents contained in the packing containers may be subject to bedegenerated with light. For example, some kinds of beverages, medicines,cosmetics and the like are, therefore, provided being contained inopaque containers formed by using a resin composition obtained byblending a resin with a coloring agent such as pigment. In recent years,however, there have been proposed a lot of containers imparted withlight-blocking property based on foaming. For example, the presentapplicant has proposed several kinds of foamed bottles having wallsfoamed by microcellular technology (e.g., see patent documents 1 to 3).

The foamed plastic formed bodies such as the above foamed bottles areexcellent in regard to their small weight and heat-insulating propertyin addition to light-blocking property accompanied, however, by aproblem of a decrease in the gas-barrier property caused by foaming. Inthe field of packing such as containers, in particular, a decrease inthe gas-barrier property is a serious problem since it permits thecontents in the containers to be oxidized and deteriorated due to thepermeation of oxygen. A decrease in the gas-barrier property caused byfoaming can, of course, be alleviated if the foaming is suppressed asmuch as possible.

The present applicant, further, has proposed many means for improvingthe gas-barrier property by vapor-depositing a film on the innersurfaces of the containers by the plasma CVD method (e.g., see a patentdocument 4). So far, however, nobody has ever attempted to a formvapor-deposited film on the foamed body. This was because in case a filmwas vapor-deposited on the foamed body, the film tended to be formedunevenly or tended to be peeled off making it difficult to obtain thegas-barrier property of the vapor-deposited film to a sufficient degree.

PRIOR ART DOCUMENTS Patent Documents

Patent document 1: JP-A-2007-022554

Patent document 2: JP-A-2007-320082

Patent document 3: JP-A-2009-262366

Patent document 4: JP-A-2006-233234

OUTLINE OF THE INVENTION Problems That the Invention is to Solve

It is, therefore, an object of the present invention to provide avapor-deposited foamed body obtained by vapor-depositing a film on thesurface of a foamed plastic formed body such as a foamed container, thevapor-deposited film being uniformly formed and being effectivelyprevented from peeling off.

Another object of the present invention is to provide a vapor-depositedfoamed body and, specifically, a vapor-deposited foamed containerfeaturing effectively improved gas-barrier property due to thevapor-deposited film and effectively suppressing a decrease in thegas-barrier property caused by foaming.

According to the present invention, there is provided a vapor-depositedfoamed body having a film vapor-deposited on the surface of a foamedplastic formed body containing foamed cells therein, wherein in thesurface of the foamed plastic formed body serving as the under-layer onwhere the film is to be vapor-deposited, the porosity of the foamedcells is suppressed to be not more than 30% in the surface layer portionto a depth of 50 μm from said surface.

In the vapor-deposited foamed body of the present invention, it isdesired that:

-   (1) The vapor-deposited film is a metal oxide film or a hydrocarbon    film formed by the plasma CVD method;-   (2) The foamed plastic formed body has been stretch-formed;-   (3) The foamed plastic formed body is a container;-   (4) The foamed plastic formed body is a container, and the film has    been vapor-deposited on the inner surface thereof that comes in    contact with the content; and-   (5) The vapor-deposited film has a thickness in a range of 10 to 50    nm.

Effects of the Invention

The vapor-deposited foamed body of the present invention has a film thatis vapor-deposited on the surface of a foamed plastic formed body inwhich foamed cells are distributed. Despite foamed cells are distributedin the interior of the formed body, the vapor-deposited film remainsclosely adhered to the surface thereof and exhibits its propertiesmaintaining stability without being peeled off.

Specifically, when the vapor-deposited foamed body is used as acontainer, the vapor-deposited film exhibits its effects to its maximumdegree. Upon forming the vapor-deposited film as described above,advantages of small weight and light-blocking property based on foamingare not impaired, a decrease in the gas-barrier property is effectivelyalleviated despite of foaming, and the quality of the contents in thecontainer is effectively prevented from being deteriorated by oxidation.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] is a sectional view of a foamed region of a vapor-depositedfoamed body obtained by vapor-depositing a film on the surface of afoamed plastic formed body according to the present invention.

[FIG. 2] is a sectional view of a foamed region of a vapor-depositedfoamed body (Comparative Example) obtained by vapor-depositing a film onthe surface of an ordinary foamed plastic formed body.

[FIG. 3] is a diagram illustrating a process for producing the foamedplastic formed body shown in FIG. 1.

[FIG. 4] is a view showing a preform used for the production of a bottlewhich is a representative example of the vapor-deposited foamed body.

[FIG. 5] is a view of a foamed bottle obtained from the preform of FIG.4.

MODES FOR CARRYING OUT THE INVENTION Vapor-Deposited Foamed Body

Referring to FIG. 1, the vapor-deposited foamed body of the presentinvention comprises a foamed plastic formed body as generally designatedat 10 containing foamed cells 1 distributed therein, and a film 15vapor-deposited on the surface thereof.

In FIG. 1, the foamed cells 1 have a flat shape but, not being limitedto this shape only, may assume a spherical shape or a shape close to thespherical shape. If the formed body 10 is a container such as a plasticbottle, however, it has usually been stretched and the foamed cells 1assume a flat shape being stretched in a direction of stretch.

The foamed cells 1 may be distributed throughout the whole formed body10, or there may be employed such a foamed structure that some of theregions are not foamed and no foamed cell 1 is distributed therein. In acontainer that will be described later, for example, the mouth portionis not usually foamed but the body portion and the bottom portion areformed and foamed cells 1 are distributed therein for preventing thesurface roughness lead to a decrease in the strength or a decrease inthe sealing property due to the foaming.

The film 15 may be vapor-deposited on the whole surfaces of the formedbody 10 but is, usually, vapor-deposited on either the outer surface orthe inner surface to meet the object (in FIG. 1, the film 15 isvapor-deposited on the inner surface). For example, if the formed body10 is a container, the film 15 that is vapor-deposited on the innersurface of the side in contact with the content, can be prevented frombeing damaged from the external side. Or the film 15 that isvapor-deposited on the outer surface can impart decorative appearance tothe container.

In the invention, the vapor-deposited film 15 is necessarily present onthe surface (either the inner surface or the outer surface) of a regionof the formed body 10 in which the foamed cells 1 are present. In theportion on where the film 15 is vapor-deposited, however, it isimportant that the foaming has been suppressed in the surface layerportion 10 a of the foamed body 10 that serves as the under-layer forthe above portion. Concretely, the region up to a depth of 50 μm fromthe surface X of the formed body 10 (surface of the under-layer) onwhich the film 15 is vapor-deposited is regarded to be the surface layerportion 10 a, and it is essential that the porosity of the foamed cells1 in this portion has been suppressed to be not more than 30% and,specifically, not more than 25%.

The porosity of the foamed cells 1 in the surface layer portion 10 a,usually, stands for a volumetric ratio of the foamed cells 1 occupyingthe unit volume of the surface layer portion. For convenience, theporosity in the present invention is an area ratio in cross section ofthe surface layer portion.

That is, upon suppressing the foaming in the surface layer portion 10 aon where the film 15 is vapor-deposited, it is allowed to effectivelyalleviate a decrease in the degree of smoothness of the under-layersurface X caused by foaming and, therefore, to turn the under-layersurface X into a surface of a high degree of smoothness (e.g., a meansurface roughness Ra of not more than 3.0 μm) that is suited forvapor-depositing the film 15 thereon. This enables the vapor-depositedfilm 15 to be closely and firmly adhered to the under-layer surface Xmaintaining a uniform thickness. Even incase an external force isexerted thereon, therefore, the stress can be homogeneously dispersedover the whole area effectively preventing the vapor-deposited film 15from being peeled off.

For example, reference should be made to FIG. 2 which shows the formedarticle 10 in which the porosity of the foamed cells 1 is exceeding 30%in the surface layer portion 10 a thereof, and the film 15 isvapor-deposited on the under-layer surface X thereof.

In this case, the foaming has not been suppressed to a sufficientdegree. Therefore, the under-layer surface X is greatly affected by anincrease in the volume of the cells 1 due to foaming, and is greatlyundulating. As a result, the vapor does not deposit evenly, thevapor-deposited film 15 does not firmly adhere to the under-layersurface X, fine gaps are formed between the under-layer surface X andthe vapor-deposited film 15, and the thickness of the vapor-depositedfilm 15 becomes non-uniform. Moreover, in case an external force isexerted, the stress concentrates locally and, therefore, the film easilypeels off. When the vapor-deposited foamed body is used as a container,in particular, these inconveniences appear as a decrease in thegas-barrier property.

In the present invention, the foaming in the surface layer portion 10 ais suppressed as described above to prevent a decrease in the closeadhesion between the vapor-deposited film 15 and the under-layer surfaceX caused by foaming, making it possible to vapor-deposit the film 15maintaining uniform thickness and effectively preventing thevapor-deposited film 15 from being peeled off by the external force.Therefore, when the present invention is applied to the containers, inparticular, a drop in the gas-barrier property is alleviated and a highgas-barrier property is attained.

In the present invention, further, the foaming has been suppressed inthe surface layer portion 10 a. As shown in FIG. 1, therefore, foamedcells la are small in size in the surface layer portion 10 a (no foamedcell la is often present therein), and foamed cells 1 b present in theregion on the lower side (region on the side of the central portion) arelarger than the foamed cells 1 a. For example, if the formed body musthave heat-insulating property and light-blocking property, then theproperties can be attained by increasing the sizes of the foamed cells.However, if it is desired to attain both the adaptability to vapordeposition and the heat-insulating property or the light-blockingproperty, the large foamed cells in the surface layer are not desired.Therefore, the present invention is most desired forming the foamedcells in small sizes in the surface layer portion only. It is, as amatter of course, allowable, depending on the required properties, evenif the foamed cells in the region on the side of the central portion aresmaller than the foamed cells in the surface layer portion provided theforming conditions are optimized.

In the present invention, there is no particular limitation on the sizeof the foamed cells 1, on the cell density or on the ratio of the foamedcells 1 in the whole foamed body 10 so far as the foaming is sosuppressed that the porosity in the surface layer portion 10 a lieswithin the above-mentioned range, and they may be selected withinsuitable ranges depending on the use of the vapor-deposited foamed body.

For instance, the size of the foamed cells 1 and the cell density may beso set as to attain improved properties (e.g., light-blocking property,small weight and heat-insulating property) required for the foaming.

In the vapor-deposited foamed body having the structure mentioned above,there is no specific limitation on the plastic material used for formingthe foamed plastic formed body 10 so far as it can be foamed or so faras it permits the vapor deposition as will be described later, and therecan be used any known thermoplastic resins.

For instance, the foamed body 10 can be formed by using:

-   -   olefin resins such as low-density polyethylene, high-density        polyethylene, polypropylene, poly 1-butene, poly        4-methyl-1-pentene or random or block copolymers such as        ethylene, propylene, 1-butene, and 4-methyl-1-pentene, and        cyclic olefin copolymers;    -   ethylene-vinyl copolymers such as ethylene-vinyl acetate        copolymer, ethylene-vinyl alcohol copolymer, and ethylene-vinyl        chloride copolymer;    -   styrene resins such as polystyrene, acrylonitrile-styrene        copolymer, ABS, and α-methylstyrene-styrene copolymer;    -   vinyl resins such as polyvinyl chloride, polyvinylidene        chloride, vinyl chloride-vinylidene chloride copolymer, methyl        polyacrylate and methyl polymethacrylate;    -   polyamide resins such as nylon 6, nylon 6-6, nylon 6-10, nylon        11 and nylon 12;    -   polyester resins such as polyethylene terephthalate (PET),        polybutylene terephthalate, polyethylene naphthalate and        copolymerized polyesters thereof;    -   polycarbonate resin;    -   polyphenylene oxide resin; and    -   biodegradable resin such as polylactic acid.

It is allowable to form the foamed body 10 by using a blend of thesethermoplastic resins, as a matter of course.

If the plastic foamed body 10 is a container, in particular, it isdesired to use a polyester resin such as PET, or an olefin resin such aspolyethylene and, most desirably, to use a polyester resin as a bottlefor beverages.

Further, the film 15 is vapor-deposited by using various kinds ofmaterials depending on the required properties. To impart opticalproperties as represented by antireflection property, for example, thefilm 15 is vapor-deposited by using a metal oxide such as SiO₂, TiO₂ orZrO₂, or by using a fluoride such as MgF₂. When the gas-barrier propertyis required in the field of packing materials such as containers,further, the vapor-deposited film is formed by depositing a metal oxidesuch as SiO₂ or a hydrocarbon such as diamond-like carbon (DLC) oramorphous carbon. Further, the film 15 may be vapor-deposited in amultilayer structure overlapping the films formed by using theabove-mentioned materials one upon another. In addition to the above,the vapor-deposited film 15 can be formed to work as an electricallyinsulating film, as a semiconductor film or as a decorative film forornamentation, by using a material suited for the purpose.

Therefore, the thickness of the vapor-deposited film 15, too, is setdepending upon the required properties to a degree that will not impairthe properties of the foamed formed body 10. To improve gas-barrierproperties required in the field of the containers such as plasticbottles, for example, the thickness of the vapor-deposited film 15 lies,preferably, in a range of 10 to 50 nm.

Production of the Vapor-Deposited Foamed Body

The vapor-deposited foamed body of the above-mentioned structure isproduced by preparing the foamed plastic formed body 10 by using theabove-mentioned plastic material suppressing the foaming in the surfacelayer portion 10 a, and vapor-depositing the film 15 on a predeterminedportion of the formed body 10.

1. Preparation of the Foamed Plastic Formed Body 10:

The foamed plastic formed body 10 is produced by forming theabove-mentioned plastic material or a composition comprising the aboveplastic material blended with suitable blending agents (e.g.,antioxidant, etc.) followed by foaming during or after the step offorming.

As the above forming means, there can be exemplified known forming meanssuch as extrusion forming, injection forming and compression forming.After the forming, it is allowable to further conduct a secondaryforming such as stretch-forming. A desired shape is realized through theabove forming.

The foaming can be conducted by chemical foaming using a foaming agentsuch as sodium bicarbonate or azo compound, or by physical foaming usingan inert gas as the foaming agent. In the present invention, it isnecessary to suppress the foaming in the surface layer portion 10 a and,therefore, it is desired to employ the physical foaming that is capableof easily suppressing the foaming and, specifically, it is most desiredto employ the microcellular foaming by which the inert gas imbibed as afoaming agent in the resin grows into bubbles to form foamed cells fromsuch a standpoint that the foamed cells are small in size and thatphysical properties such as strength and the like are little affected bythe foamed cells.

The foamed plastic formed body that is foamed relying on the abovemicrocellular foaming can be obtained by using known methods (e.g.,patent documents 1 to 3 and WO2009/119549) which the present applicanthave proposed so far and by so adjusting the foaming conditions that thefoaming in the surface layer portion 10 a satisfies the above-mentionedporosity.

FIG. 3 illustrates a process for producing the foamed plastic formedbody 10 by utilizing the microcellular foaming.

Namely, according to the above method as shown in FIG. 3, a gas-imbibedformed body is prepared in which the inert gas (nitrogen gas or carbondioxide gas) that serves as the foaming agent is dissolved, and thegas-imbibed formed body is foamed by heating it to a degree (e.g.,melting point or softening point thereof) by which the formed body isnot thermally deformed to thereby obtain a foamed plastic formed body 10of a desired shape. After the foaming, further, the secondary forming isconducted, such as stretch-forming, to obtain the foamed plastic formedbody 10 of the final shape. In the present invention, the foamingconditions are set in the step of forming so that the foaming in thesurface layer portion 10 a satisfies the above-mentioned porosity.

First, the gas-imbibed formed body imbibing the inert gas is obtained byforming an unfoamed formed body by the above-mentioned known formingmeans, and placing the unfoamed formed body in an inert gas atmosphereof a high pressure under a condition of being heated or not heated. Thehigher the temperature, the smaller the amount of gas dissolved thereinbut the larger the imbibition rate is. The lower the temperature, thelarger the amount of gas dissolved therein but the longer the timeneeded for the imbibition.

It is, further, allowable to obtain the formed body imbibing the inertgas by feeding the inert gas under high pressure to the melt-kneadingportion of the forming machine and directly feeding the plastic materialfor forming in which the inert gas is dissolved to the forming such asinjection-forming. In this case, to obtain the formed body free ofdefective appearance such as swirl marks by preventing foaming in theinjection-forming machine, it is desired to conduct the forming byinjection-filling the plastic material for forming in which the inertgas is dissolved while maintaining the pressure in the mold cavity inwhich a high pressure is maintained as proposed in WO2009/119549 filedby the present applicant.

The foaming is conducted by heating the gas-imbibing formed body that isobtained as described above. Here, in the present invention, it isnecessary to suppress the foaming in the surface layer portion 10 a. Theprocess for obtaining the foamed plastic formed body 10 by suppressingthe foaming can be divided, as shown in FIG. 3, into a process thatexecutes the foaming after having released the gas and a process thatcontrols the heating during the foaming.

Referring to FIG. 3, the gas-releasing process releases the inert gasfrom the surface layer portion 10 a of the gas-imbibing formed body(a-1) and, next, conducts the foaming by heating (a-2).

The gas is released from the surface layer portion 10 a by, for example,placing the gas-imbibing formed body taken out in a cooled andsolidified state from the mold under a normal pressure (atmosphericpressure) for a predetermined period of time so that the inert gas isreleased from the surfaces thereof and, next, heating the formed body soas to be foamed.

Upon releasing the gas as described above, the inert gas is no longerdissolved or the concentration of the inert gas is very decreasing inthe surface layer portion 10 a. By conducting the heating under thiscondition, therefore, it is allowed to suppress the foaming in thesurface layer portion 10 a. This is because the porosity decreases inthe surface layer portion 10 a where the gas concentration is low, as amatter of course. The amount of gas remaining in the surface layerportion 10 a can be adjusted depending on the time in which thegas-imbibing formed body is placed under the atmospheric pressure forreleasing gas (substantially, depending on the time until the foaming byheating is effected next time). Namely, the longer the time of placingthe formed body under the open atmosphere, the closer to zero the amountof gas in the surface layer portion 10 a is. The shorter the time ofplacing the formed body under the open atmosphere, the larger the amountof gas in the surface layer portion 10 a is and the higher the porosityis. Here, attention should be given to that if the formed body is placedunder the open atmosphere for unnecessarily longer periods of time, thenthe foaming does not take place or takes place to a very small degreemaking it difficult to achieve the object of foaming.

In the surface layer portion 10 a, the foaming may be suppressed in onlya portion on where the film 15 is vapor-deposited. Therefore, means maybe employed so as to expose only the potion where the film 15 isvapor-deposited to the atmosphere to release the gas while coveringother portions so will not be exposed to the atmosphere. This makes itpossible to selectively release the gas from only the portion on wherethe film 15 is to be vapor-deposited. For example, if the film isvapor-deposited on the inner surface side of the formed body 10 as shownin FIG. 1, then the gas may be released from at least the inner surfaceside of the formed body 10.

After the inert gas serving as the foaming agent was released from thesurface layer portion 10 a as described above, the formed body is heatedand foamed (a-2) to obtain the foamed plastic formed body 10 suppressingfoaming in the surface layer portion 10 a.

Due to the heating in the step (a-2), the inert gas inflates to generateand grow the cells; i.e., foaming is attained. The heating temperatureis such that the formed body is not thermally deformed but is at leasthigher than the glass transition point (Tg) of the resin. The higher theheating temperature, the larger the size of the foamed cells and thehigher the porosity is. However, there is no inert gas in the surfacelayer portion 10 a to generate the foamed cells. Therefore, attentionshould be given to that the bubbles do not so grow in the region underthe surface layer portion 10 a as to infiltrate into the surface layerportion 10 a to increase the porosity therein.

Suppressing the foaming based on the above method is particularlyadvantageous when it is attempted to suppress the foaming in both theinner surface and the outer surface since the gas has already beenreleased from the surface layer portion 10 a. This also gives such anadvantage that the porosity in the surface layer portion 10 a can bedecreased to substantially zero.

The heating for foaming is not specifically limited, and can be carriedout by any means such as blowing the hot air, using an infrared-rayheater or a high frequency heating, or an oil bath.

The heating for foaming needs not be effected for the regions where nofoaming is necessary, as a matter of course. For example, the mouthportion of the container must avoid the foaming that causes a decreasein the strength or a decrease in the smoothness (decrease in the sealingproperty). Therefore, if the mouth portion, too, is imbibing the gas,the heating is selectively effected for only the portions that requirefoaming so that no foaming takes place in the mouth portion. When amultiplicity of layers are injected such that the mouth portion isformed from a non-foaming resin and at least part of the body portion isformed from a foaming resin and, thereafter, when the mouth portion iscrystallized, then there is no need of avoiding the heating for themouth portion.

In another process, the gas is not released from the surface layerportion 10 a, and the gas-imbibing formed body is directly introducedinto the foaming step (b) to heat and foam the gas-imbibing formed body.

The heating and foaming are conducted in basically the same manner as inthe step (a-2) that is conducted after the gas is released with,however, a great difference in regard to that the surface of the surfacelayer portion 10 a is not positively foamed by heating. For example, ifthe film 15 is to be vapor-deposited on the inner surface side of theformed body 10 as shown in FIG. 1, then the heating may be effected fromouter surface side. Or if the heating is effected from the inner andouter surface sides, then the heating on the inner surface side may beweakened. That is, the foaming may be attained by so effecting theheating that the temperature in the surface layer portion 10 a does notbecome higher than the glass transition point or the temperature thereinis not maintained to be higher than the glass transition point for longperiods of time. Due to the above heating and foaming, the temperaturebecomes sufficiently high (to a degree by which the formed body 10 isnot deformed) in the portions other than the surface layer portion 10 a,and the foamed cells grow into a large size. In the surface layerportion 10 a, however, the foamed cells are limited from generating orgrowing.

When the foaming in the surface layer portion 10 a is controlled by theabove means, the foaming takes place due to the conduction of heat tothe side of the surface layer portion 10 a from the surface on the sideopposite to the surface layer portion 10 a (surface X under thevapor-deposited film 15) in which the foaming is controlled. Therefore,the foamed cells located on the side opposite to the surface layerportion 10 a have the largest size, and the size of the foamed cellsdecreases toward the surface layer portion 10 a (so-called inclinedfoaming). If it is attempted to decrease the weight by foaming byincreasing the porosity in the foamed formed body 10, then the abovemeans is particularly advantageous in such cases where the heatingcannot be effected from the one side though there remains a probabilitythat the porosity cannot be decreased down to 30% or smaller in thesurface layer portion 10 a.

The heating step (a-2) conducted after the gas has been released, too,may employ the above method of effecting the heating from the one sideor the method of weakening the heating from the inner surface side.

As described above, foaming is suppressed in the surface layer portion10 a, and there is obtained the foamed plastic formed body 10 having thefilm 15 vapor-deposited on the surface layer portion 10 a.

As shown in FIG. 3, further, the formed body 10 can be subjected to thesecondary forming such as stretch-forming. In the case of suchcontainers as bottles or cups, for example, the foamed plastic formedbody 10 obtained through the above steps is a primarily formed body(preform) which is, thereafter, subjected to the stretch-forming so asto be shaped into a container which is the secondarily formed body.Therefore, the foamed cells 1 (1 a, 1 b) of flat shapes shown in FIG. 1are those of the secondarily formed body that is stretch-formed. Thefoamed cells 1 that have not been subjected to the secondary formingsuch as stretch-forming assume a shape close to nearly a sphericalshape.

When the secondary forming is conducted as described above, it isimportant that the foaming has been suppressed in the surface layerportion of the primarily formed body so that the porosity in the surfacelayer portion 10 a after the secondary forming lies in theabove-mentioned range. This is because the film 15 is vapor-deposited onthe surface of the secondarily formed body and, besides, depending onthe secondary forming such as stretching, the thickness decreases andthe position that used to be 50 μm deep from the surface may vary.

FIG. 4 shows a preform for forming a bottle which is the primarilyformed body.

The preform generally designated at 50 has the shape of a test tube andis forming, at its upper portion, a neck portion 51 having a screwthread 51 a and a support ring 51 b. A body portion 53 and a bottomportion 55 are formed on the lower side of the neck portion 51.

In the case of a plastic bottle, in general, if a gas is dissolved in aportion such as the mouth portion on where the screw thread has beenformed, an attempt of foaming the portion such as the mouth portioncauses a decrease in the strength or a decrease in the sealing propertydue to roughened surfaces. Therefore, the neck portion 51 of the preform50 is not subjected to the above-mentioned heating for forming, but thebody portion 53 and the bottom portion 55 are foamed, i.e., are foamedby heating to form a foamed region where there are distributed foamedcells of a spherical shape or of a shape close to the spherical shape.If a multiplicity of layers is injected so that the mouth portion isformed from a non-foaming resin and at least part of the body portion isformed from a foaming resin and if, thereafter, the mouth portion iscrystallized, then there is no need of avoiding the heating for themouth portion.

In case the film is to be vapor-deposited on the plastic bottle in amanner that the vapor-deposited film can be prevented from being damagedby the external pressure or the like, then the film is vapor-depositedon the inner surface of the bottle. In this case, therefore, the heatingis so effected that the foaming is suppressed in the surface layerportion on the inner surface side of the preform 50. Even if the film 15has not been vapor-deposited, it is desired that the bottle that isfinally obtained has smoothness on the outer surface, too. It is,therefore, desired that the surface layer portion on the outer surfaceside, too, is suppressed from being foamed by the above-mentionedmethod. Further, if the film 15 is vapor-deposited on the outer surfaceside so that the surface of the plastic bottle exhibits brilliantspecular luster, then the heating is so effected that the foaming issuppressed in the surface layer portion on the outer surface side of thepreform 50. In this case, too, the foaming may be suppressed both in thesurface layer portion on the outer surface side and in the surface layerportion on the inner surface side, as a matter of course.

If the foaming is effected in order to impart light-blocking property toprevent the content from being degenerated, it is desired that theamount of gas that is imbibed, the heating temperature and the heatingtime for foaming are so adjusted that the density of the foamed cellsbecomes about 10⁵ to about 10¹⁰ cells/cm³ in the central portions,except the surface layer portion where the foaming is limited, in thefoamed regions (body portion 53 and bottom portion 55) of the preform 50which is the primarily formed body, that the mean diameter thereof(equivalent circle diameter) becomes about 3 to about 50 μm and that thenumber of bubbles is not less than 17 in the direction of thickness ofthe bottle after it has been blow-formed.

A foamed bottle 60 (secondarily formed body) of a shape shown, forexample, in FIG. 5 is obtained by stretch-forming (blow-forming) theabove preform 50. The foamed bottle 60 is forming a neck portion 61having a screw thread 61 a and a support ring 61 b corresponding to theabove preform 50, and is forming a body portion 63 and a bottom portion65 on the lower side of the neck portion 61. The body portion 63 and thebottom portion 65 are the foamed regions in which the foamed cells aredistributed.

The foamed bottle 60 has been stretch-formed and, therefore, the foamedcells 1 which were nearly of a spherical shape in the preform 50 are nowassuming a flat shape being stretched in the direction of stretch asshown in FIG. 1.

In the above foamed bottle 60, the film 15 is vapor-deposited on theinner surface thereof. Therefore, the foaming has been so suppressedthat the porosity lies in the above-mentioned range (not more than 30%and, specifically, not more than 25%) in the surface layer portion 10 athat has the under-layer surface X (on where the vapor deposits).

There is no need of limiting the foaming in the outer surfaces of thefoamed regions (body portion 63 and bottom portion 65) of the foamedbottle 60 unless the film 15 is not vapor-deposited thereon. On theseregions, too, however, it is desired to form an unfoamed skin layer(layer without substantially containing any foamed cell) and,specifically, on the outer surface of the body portion 63 to improvesmoothness and, therefore, to improve printability and easiness forsticking labels. The skin layer can be easily formed by releasing thegas prior to conducting the foaming.

There is no need of limiting the foaming in the inner part (region whichis not the surface layer) of the foamed bottle 60, and the porosity maybe set depending on the object. If it is desired to obtain a lowlylight-blocking bottle, then the number of bubbles may be decreased inthe direction of thickness of the bottle. Further, the central regionmay be left unfoamed by adjusting the forming conditions.

The foamed preform 50 is stretch-formed by blow-forming the preformwhile heating it at a temperature higher than a glass transition pointof the resin but lower than a melting point thereof. Depending on thestate of the container or the preform, however, the stretch-forming maybe effected relying on the vacuum forming as represented by theplug-assist forming. For example, if it is attempted to produce a foamedcontainer of the shape of a cup, the foamed preform (primarily formedbody) of the shape of a plate or a sheet is formed according to themethod described above, and is subjected to the secondary forming suchas the plug-assist forming. Irrespective of which stretch-forming meansis employed, the foaming in the surface layer portion may be sosuppressed that the porosity is not larger than a predetermined value inthe surface layer portion 10 a in the portion that serves as theunder-layer surface X (on where the vapor deposits) on where the film 15is to be vapor-deposited.

The secondary forming such as blow forming or vacuum forming may beconducted relying on a means that has been known per se., as a matter ofcourse.

For example, in the blow forming which executes the stretching in twodirections of the axial direction (direction of height) and thecircumferential direction, the axial direction is, usually, thedirection of a maximum stretch. Therefore, the porosity in the surfacelayer portion 10 a may be rendered to lie in a predetermined range byforming foamed cells 1 of a flat shape having a suitable length (maximumlength in the direction of stretch) and an aspect ratio by adjusting thestretching ratio in the axial direction to lie in a suitable range.

In the foamed plastic formed body 10 obtained as described above, thefilm 15 is vapor-deposited on the vapor deposition surface (under-layersurface X which is the surface of the surface layer portion 10 a) inwhich the foaming has been suppressed.

2. Vapor-Depositing the Film 15:

According to the invention, the film 15 is vapor-deposited by a knownmeans, i.e., physical vapor deposition such as vacuum evaporation,sputtering or ion plating, or chemical vapor deposition such as plasmaCVD depending on properties such as heat resistance of the foamedplastic formed body 10 and the form thereof, on the position on wherethe film 15 is to be deposited and on the use of the formed body 10.

The vapor-deposited foamed body of the invention is very advantageousfrom the standpoint of improving gas-barrier property byvapor-depositing the film 15 (from the standpoint of avoiding a decreasein the gas-barrier property caused by foaming) . Most of thevapor-deposited foamed bodies assume the form of the bottle 60 describedabove. In such packing containers, it is desired that the film 15 isvapor-deposited by the plasma CVD that can be executed at a relativelylow temperature from the standpoint of the container material (usually,polyester or polyolefin) and, most desirably, the film 15 isvapor-deposited by the microwave plasma CVD that forms the film bygenerating a plasma by feeding microwaves into the container. A highfrequency plasma CVD, too, can be applied requiring, however, the bodyportion of the container on where the film is to be deposited to bepositioned between the electrodes and, therefore, requiring a complexapparatus, which is not so much desired.

The plasma CVD is desired not only when it is attempted to vapor-depositthe film 15 on the inner surface of the packing container but also whenit is attempted to vapor-deposit the film 15 on the outer surface of thepacking container in order to impart decorative appearance to thesurface of the packing container, i.e., to impart brilliant specularluster thereto, and the microwave plasma CVD is most desired.

Representative examples of the vapor-deposited film 15 for improvinggas-barrier property include metal oxide films such as SiO₂, andhydrocarbon films such as diamond-like carbon (DLC) and amorphouscarbon. The film 15 can be vapor-deposited on the inner surface of thecontainer by the microwave CVD relying on a means that has been knownper se., e.g., relying on a method disclosed in JP-A-2006-233234 filedby the present applicant.

If a metal oxide film such as SiO₂ is to be deposited, there can beused, as the reaction gas, an organometal compound, such as:

a silane compound like hexamethyldisilane, vinyltrimethylsilane,vinyltrimethoxysilane or tetramethoxysilane;

an organoaluminum compound like trialkyl aluminum; or an organotitaniumcompound; depending on the kind of the metal with which the film is tobe formed. The organometal compound gas is used being suitably mixedwith an oxidizing gas such as oxygen or a carrier gas such as nitrogen.

If a hydrocarbon type film is to be deposited, there is preferably used,as the hydrocarbon source, a hydrocarbon compound such as unsaturatedaliphatic hydrocarbon or aromatic hydrocarbon that can be easilygasified. Representative examples of the unsaturated aliphatichydrocarbon include:

alkenes such as ethylene, propylene, butene and pentene; and

alkynes such as acetylene and methylacetylene.

Representative examples of the aromatic hydrocarbon include benzene,toluene and xylene. Usually, the unsaturated aliphatic hydrocarbons aredesired and, specifically, ethylene and acetylene are most desired. Thehydrocarbon source gas is used as a reaction gas being suitably mixedinto a gas of a compound (e.g., oxygen-containing gas such as methanol,ethanol or acetone) that introduces polar groups into the film toimprove close adhesion of the formed body 10 to the under-layer surfaceX.

The plasma CVD by using the above reaction gas is conducted in a mannerof, for example, holding a container upside down in a plasma treatmentchamber that has been shielded with a suitable metal wall, inserting agas pipe in the mouth portion of the container to feed the reaction gasinto the container, deaerating the interior of the container in thisstate to a vacuum degree that enables a plasma to be generated,deaerating the exterior of the container, too, to such a vacuum degreethat does not cause the container to be deformed, feeding microwavesinto the chamber (into the container) through a conduction pipe such aswaveguide, generating a plasma by using the energy of microwaves and, atthe same time, feeding the above-mentioned reaction gas through a gaspipe to cause the reaction so as to form the film.

In depositing the film as described above, it is allowable to change thecomposition of the vapor-deposited film 15 by, for example, adjustingthe composition of the reaction gas or the output of microwaves. Forexample, if a film of a metal oxide such as SiO₂ is to be deposited, theamount of the organic component in the film can be increased bydecreasing the output thereby to improve flexibility or softness of thefilm and to, further, improve close adhesion to the under-layer surfaceX. Therefore, the film is deposited starting, first, with a low outputwhich is then gradually increased to form a film having a high degree ofoxidation and a high gas-barrier property.

The film 15 is deposited on a predetermined surface of the foamedplastic formed body 10 (e.g., bottle 60 of FIG. 5) in a manner asdescribed above. In this invention, foaming has been suppressed in thesurface layer portion 10 a that is forming the under-layer surface X onwhere the film 15 is vapor-deposited. Therefore, the film can behomogeneously deposited having improved smoothness; i.e., the film 15 isvapor-deposited being highly and closely adhered to the under-layersurface X effectively solving the problem of peeling.

According to the present invention, the advantage of foaming can beutilized to a maximum degree and, at the same time, the film can bevapor-deposited in a highly and closely adhered manner despite offoaming, effectively preventing the peeling and effectively exhibitingthe advantages of the vapor-deposited film.

If the invention is applied to, for example, packing containers such asbottles, characteristics due to foaming, such as small weight andlight-blocking property can be effectively exhibited. Besides, thevapor-deposited film works to effectively alleviate a decrease in thegas-barrier property caused by foaming and, further, works to improvethe gas-barrier property.

EXAMPLES

Described below are Examples and Comparative Examples, and their resultsare shown in Table 1. As for the amounts of oxygen permeating throughthe bottles in Table 1, the gas-barrier property was judged to befavorable if the amount of oxygen permeating through the bottle of afterthe vapor deposition was smaller than one-half the representativeamount, i.e., 0.06 cc/bottle/day of oxygen permeating through the bottleof before the vapor deposition, i.e., if the amount of oxygen permeatingthrough the bottle of after the vapor deposition was smaller than 0.03cc/bottle/day.

Example 1

A PET resin for bottle containing 0.15% of a nitrogen gas and having anintrinsic viscosity (IV) of 0.84 dL/g was injected into a mold cavitymaintaining a pressure therein of 5 MPa by blowing high-pressure air anda temperature of 30° C. and, thereafter, the pressure therein wasmaintained at 50 MPa for 18 seconds. After another 12 seconds havepassed, the mold was opened. There was obtained a preform for containerof the shape of a test tube in a substantially unfoamed state in whichthe gas has been dissolved and having a smooth surface and an overalllength of about 110 mm.

The preform was, further, heated and foamed, and was directlyblow-formed to obtain a foamed blow-formed bottle having a thickness inthe body portion of about 600 μm and a capacity of about 500 ml. Theheating was conducted from both the outer surface side and the innersurface side, and the heating condition was so adjusted that thetemperature was 99° C. on the inner surface side of the preform (at aportion 45 mm away from the nozzle top panel).

After the blow-formed bottle was set in the chamber, the interior andexterior of the bottle were evacuated. An HMDSO (hexamethyldisiloxane)was introduced as the reaction gas and after a predetermined pressurewas reached, microwaves of 2.45 GHz were introduced to form an SiOxfilm. From the following SEM photograph, the thickness of the film atthis moment was found to be about 20 nm.

The obtained bottle having the film vapor-deposited on the inner surfacethereof was measured for its amount of oxygen permeation by using anoxygen barrier testing machine (OX-TRAN manufactured by MOCON Co.) (37°C.) to find that the amount of oxygen that has permeated through was0.003 cc/bottle/day, which was a favorable result (before the vapordeposition, it was 0.06 cc/bottle/day).

By using the scanning electron microscope (SEM), the cross section ofthe bottle body portion was photographed and by using an image analysissoftware (Mac-View manufactured by Mountec Co.) plated in the market,the area ratio of the foamed cells was found in cross section of theinner surface layer portion of the bottle body portion (range from thesurface of the foamed plastic formed body serving as the under-layer forvapor-depositing the film down to a depth of 50 μm). The averageporosity was calculated to be 8% on the average at three points. Forcomparison, further, the area ratio of the foamed cells was found incross section of the outer surface layer portion of the bottle bodyportion (range from the surface of the foamed plastic formed body on theside that is not serving as the under-layer for vapor-depositing thefilm down to a depth of 50 μm), and from which the average porosity wascalculated to be 12% on the average at three points.

Example 2

A preform was formed, a bottle was formed, and a film wasvapor-deposited thereon in the same manner as in Example 1 but soadjusting the heating conditions that the temperature was 102° C. on theinner surface side of the preform of when it was being heated.

The amount of oxygen that has permeated through the obtained bottlehaving its inner surface vapor-deposited was as good as 0.004cc/bottle/day (before the vapor deposition, the amount was 0.06cc/bottle/day).

The average porosity was 19% in the inner surface layer portion of thebottle body portion, and was 24% in the outer surface layer portionthereof.

Example 3

A preform was formed, a bottle was formed, and a film wasvapor-deposited thereon in the same manner as in Example 1 but soadjusting the heating conditions that the temperature was 104° C. on theinner surface side of the preform of when it was being heated.

The amount of oxygen that has permeated through the obtained bottlehaving its inner surface vapor-deposited was as good as 0.007cc/bottle/day (before the vapor deposition, the amount was 0.07cc/bottle/day).

The average porosity was 25% in the inner surface layer portion of thebottle body portion, and was 32% in the outer surface layer portionthereof.

Example 4

First, a preform was formed in the same manner as in Example 1. A bottlewas formed and a film was vapor-deposited in the same manner as inExample 1 but at the time of heating the preform prior to blowing,adjusting the heating conditions in a manner that the heating was strongfrom the outer surface side but was weak from the inner surface side soas to positively foam the regions other than the vapor depositionsurface (inner surface). The temperature was 110° C. on the outersurface of the preform and was 94° C. on the inner surface thereof ofwhen it was being formed into the bottle.

The amount of oxygen that has permeated through the obtained bottlehaving its inner surface vapor-deposited was as good as 0.013cc/bottle/day (before the vapor deposition, the amount was 0.08cc/bottle/day).

The average porosity was 11% in the inner surface layer portion of thebottle body portion, and was 39% in the outer surface layer portionthereof.

Example 5

First, a preform was formed in the same manner as in Example 1. Thepreform that was formed was stored for about one week to let the gasdissolved near the surface layer portion to be released to theatmosphere. Thereafter, a bottle was formed and a film wasvapor-deposited in the same manner as in Example 1 but so adjusting theheating conditions that the temperature was 108° C. on the inner surfaceside of the preform of when it was being heated.

The amount of oxygen that has permeated through the obtained bottlehaving its inner surface vapor-deposited was as good as 0.01cc/bottle/day (before the vapor deposition, the amount was 0.09cc/bottle/day).

No bubble was observed in the inner surface layer portion of the bottlebody portion (average porosity was 0%).

Example 6

First, a preform was formed and a bottle was formed therefrom in thesame manner as in Example 1. After the bottle was set in the chamber, adiamond-like carbon (DLC) film was deposited under the same film-formingconditions as those of Example 1 but changing the reactive gas speciesinto acetylene. From a SEM photograph, the thickness of the DLC film wasabout 20 nm.

The amount of oxygen that has permeated through the obtained bottlehaving its inner surface vapor-deposited was as good as 0.003cc/bottle/day (before the vapor deposition, the amount was 0.06cc/bottle/day).

The average porosity was 8% in the inner surface layer portion of thebottle body portion, and was 12% in the outer surface layer portionthereof.

Comparative Example 1

A preform was formed, a bottle was formed, and a film wasvapor-deposited thereon in the same manner as in Example 1 but soadjusting the heating conditions that the temperature was 109° C. on theinner surface side of the preform of when it was being heated.

The amount of oxygen that has permeated through the obtained bottlehaving its inner surface vapor-deposited was 0.05 cc/bottle/day, andgood barrier property was not obtained (before the vapor deposition, theamount was 0.08 cc/bottle/day).

The average porosity was 32% in the inner surface layer portion of thebottle body portion, and was 41% in the outer surface layer portionthereof.

Comparative Example 2

A preform was formed, a bottle was formed, and a film wasvapor-deposited thereon in the same manner as in Example 1 but soadjusting the heating conditions that the temperature was 112° C. on theinner surface side of the preform of when it was being heated.

The amount of oxygen that has permeated through the obtained bottlehaving its inner surface vapor-deposited was 0.07 cc/bottle/day, and agood barrier property was not obtained (before the vapor deposition, theamount was 0.09 cc/bottle/day).

The average porosity was 37% in the inner surface layer portion of thebottle body portion, and was 47% in the outer surface layer portionthereof.

Comparative Example 3

A preform was formed, a bottle was formed, and a film wasvapor-deposited thereon in the same manner as in Example 1 but soadjusting the heating conditions that the temperature was 118° C. on theinner surface side of the preform while weakening the heating from theouter surface side of the preform to suppress the foaming on the outersurface side thereof.

The amount of oxygen that has permeated through the obtained bottlehaving its inner surface vapor-deposited was 0.08 cc/bottle/day, and agood barrier property was not obtained (before the vapor deposition, theamount was 0.09 cc/bottle/day).

The average porosity was 38% in the inner surface layer portion of thebottle body portion, and was 18% in the outer surface layer portionthereof.

In Comparative Examples 1, 2 and 3, favorable gas-barrier property wasnot obtained presumably because of the following reasons. If theporosity is high near the vapor deposition surface (surface of thefoamed plastic formed body serving as the under-layer on where the filmis to be vapor-deposited), the resin density becomes relatively low inthe resin portions around the bubbles and the resin becomes locallythin. Besides, the vapor deposition often becomes rugged to a largeextent being affected by the growth of bubbles. If the thickness locallydecreases or if there exists a rugged skin layer, the thickness of thevapor-deposited film becomes non-uniform on the vapor depositionsurface, and the vapor-deposited film is often locally peeled off due tolocal thermal deformation or the external force during the vapordeposition. The irregular thickness or the local peeling of thevapor-deposited film presumably accounts for the exhibition of poorgas-barrier property. It is considered that there are values such asthreshold values for maintaining the uniformity of adhesion of thevapor-deposited film or for maintaining the film strength. If the filmis weakly adhered or peeled off even locally, then the gas-barrierproperty decreases over the bottle as a whole; i.e., the gas-barrierproperty sharply decreases with the porosity of about 30% as a boundary.

TABLE 1 Porosity in bottle Inner surface layer (%) surface Outer Amountof oxygen temp. surface Inner permeating through of when Kind of layersurface bottle PF is vapor- (non- layer (cc/bottle/day) heated depositeddeposition (deposition Before After (° C.) film surface) surface)deposited deposited Evaluation Ex. 1 99 SiOx 12 8 0.06 0.003 good Ex. 2102 SiOx 24 19 0.06 0.004 good Ex. 3 104 SiOx 32 25 0.07 0.007 good Ex.4 94 SiOx 39 11 0.08 0.013 good Ex. 5 108 SiOx 0 0 0.09 0.01 good Ex. 699 DLC 12 8 0.06 0.003 good Comp. 109 SiOx 41 32 0.08 0.05 poor Ex. 1Comp. 112 SiOx 47 37 0.09 0.07 poor Ex. 2 Comp. 118 SiOx 18 38 0.09 0.08poor Ex. 3

DESCRIPTION OF REFERENCE NUMERALS

-   1: foamed cells-   10: foamed plastic formed body-   10 a: surface layer portion-   15: vapor-deposited film

1. A vapor-deposited foamed body having a film vapor-deposited on the surface of a foamed plastic formed body containing foamed cells therein, wherein in the surface of the foamed plastic formed body serving as the under-layer on where the film is to be vapor-deposited, the porosity of the foamed cells is suppressed to be not more than 30% in the surface layer portion to a depth of 50 μm from said surface.
 2. The vapor-deposited foamed body according to claim 1, wherein said vapor-deposited film is a metal oxide film or a hydrocarbon film formed by the plasma CVD method.
 3. The vapor-deposited foamed body according to claim 1, wherein said foamed plastic formed body has been stretch-formed.
 4. The vapor-deposited foamed body according to claim 1, wherein said foamed plastic formed body is a container.
 5. The vapor-deposited foamed body according to claim 1, wherein said foamed plastic formed body is a container, and said film has been vapor-deposited on the inner surface thereof that comes in contact with the content.
 6. The vapor-deposited foamed body according to claim 1, wherein said vapor-deposited film has a thickness in a range of 10 to 50 nm. 